Solving the historic riddle of dolphin strandings

Friday

Jun 29, 2012 at 2:00 AM

At the Cape Cod Museum of Natural History in Brewster, earlier this month, Brian Sharp, stranding coordinator for the International Fund for Animal Welfare in Yarmouthport, told a full auditorium that the mass stranding of common dolphins last winter came in two waves.

At the Cape Cod Museum of Natural History in Brewster, earlier this month, Brian Sharp, stranding coordinator for the International Fund for Animal Welfare in Yarmouthport, told a full auditorium that the mass stranding of common dolphins last winter came in two waves. In the first few days, it spiked from one to 67. From Jan. 12 to Feb. 16, 179 animals beached themselves.

The next wave occurred from Feb 17 to April 3. In 47 days ,37 more animals came shoreward to mire in the flats. Out of the total of 216 stranded creatures, Sharp said 118 were found dead, 98 alive. Of those 12 died and eight were humanely euthanized, deemed too sick to reenter the water. Five of those released, re-stranded. Seventy-three in total re-entered the oceans.

Strandees are taken in red stretchers on wide-wheeled carts to shore, laid in a star pattern facing inward to comfort each other with vocalizations, then checked out in two IFAW trailers used as labs, hospitals and transportation; weighed, blood taken, ultrasounds given to determine pregnancy, blood gases investigated for bubbles indicating rapid ascent causing cetacean bends, checked for lesions. Sexed. Two veterinarians supervised necropsies of 21 dead dolphins, drawing blood and culturing tissue.

Sharp said that while some dolphins floated free of their own accord (at the Barnstable-Yarmouth line he witnessed eight stranding and releasing themselves), many more died shortly after beaching, heart rates high, stressed by gravity’s pressure.

Healthy animals were released at Herring Cove, Provincetown (where, Sharp said, the most releases on earth have occurred). But winds interfered, so IFAW decided to stage re-entries in Sandwich at Scusset State Park beach. On Feb. 9, five stranding dolphins off of Sandy Neck were brought to the parking lot with the help of Barnstable resource officers and a truck. Three died, but two were successfully taken to Scusset where waters are deep enough for the dolphins to swim off without re-stranding. Fifteen others were released there, contributing to the 74 percent success rate in salvation, which Sharp says is highest in IFAW’s history.

Animals are always tagged with an identification number. Nineteen animals, given additional new satellite tags which self-release in 30 to 40 days, were set loose in groups which swam to Maryland; to northern Maine; to the continental shelf 320 miles beyond southeast Nantucket. Some were seen around Provincetown this month. (NOAA estimates no more than 120,000 common dolphins are in the sea from Florida to the Bay of Fundy.)

One hundred twenty-seven dolphins had no chance to strand, because IFAW tried other new tactics: Alarm went as usual via the eyes and telephones of 30 to 60 volunteers to the professional staff of six biologists, but then the dolphins were herded away from shore with inflatable boats rigged with pingers making unpleasant noises.

While many test results will take another year to come in, what IFAW knows so far is there was no through-line of common disease, but almost every disease, virus, bacteria, fungus that a dolphin can get showed up in individuals. As a whole, the population was fairly unhealthy. There were, atypically, far more males than females, and animals were much larger than common dolphins seen before in strandings.

Scientists question why common dolphins, deep water animals which swim in flexible groups from six to eight to 600 to thousands, had decided to come in closer to shore than usual.

They ask: Was ill health due to pollution? Is it new antibiotic resistance found globally in marine mammals? Did they come in because patterns prey such as herring and sand launce have changed? Does noise from seismic events or oil drilling drive them in? Bad weather?

Audience members wondered: Was it submarine or early warning acoustical devices in play in the Gulf of Maine occurring during heightened tensions with Iran in the Gulf of Hormuz? Is it climate change? Was sickness due to the Boston outfall pipe – weakening immune systems? IFAW has said no naval activities occurred in our area during the stranding; the other questions have no answers as yet.

What biologists do know is that once the animals came closer in to Cape Cod Bay, from Sandy Neck to Dennis to Brewster to Wellfleet Harbor where the highest amount of strandings occurred, they get caught. In Wellfleet’s case, a hook within a hook becomes very difficult to navigate out of, while in areas such as Brewster, half-mile expanses of flats trap animals when tides rapidly recede.

What they do know is that the Cape is a hot spot for stranding with 17 kinds of cetaceans and five of seals, and that while marine mammal strandings spiked between 2005 and 2007 and 2009 to 2010 -- and pilot whales in particular have been stranding on the Cape since Indian times (with a big event in 2002) -- the average a year for seals and cetaceans combined is 228 and thus, last year’s drama remains both historic and a riddle.

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